We’ve always known that dolphins are some of the coolest and smartest creatures in the sea. The similarities they share with humans are remarkable, and a new study highlights yet another striking similarity: dolphins form friendships based on shared interests, and they can form close bonds for years.

The findings, published in the Proceedings of the Royal Society B by an international team of researchers from the Universities of Bristol, Zurich and Western Australia adds even more insight into the social habits of dolphins.Image credits: NOAA.

The study followed the population of Indo-Pacific bottlenose dolphins in Shark Bay, a World Heritage area in Western Australia — the only location where dolphins have been observed using marine sponges as foraging tools. These “sponger” dolphins use the technique to forage for food in deeper waters by using the sponges to protect their noses as they hunt.

Using behavioral, genetic, and photographic data collected from 124 male dolphins during the winter months in Shark Bay from 2007 to 2015, the team analyzed a subset of 37 male dolphins, comprising 13 spongers and 24 non-spongers. They found that the spongers spent more time associating with fellow spongers than the non-spongers.

“Foraging with a sponge is a time-consuming and largely solitary activity so it was long thought incompatible with the needs of male dolphins in Shark Bay – to invest time in forming close alliances with other males,” says Dr Simon Allen, a co-author of the study and senior research associate at Bristol’s School of Biological Sciences. “This study suggests that, like their female counterparts and indeed like humans, male dolphins form social bonds based on shared interests.”

Bottlenose dolphin with a sponge in Shark Bay. Image credits: Simon Allen.

Most dolphin species live in pods consisting of two to thirty animals. Between these groups, they tend to show empathetic, cooperative and altruistic behaviors. It has also been found that dolphins can migrate between pods, creating a complex social network. Also proven is that dolphins can communicate with other cetaceans through sounds, clicks and songs. So, really, given dolphins history, the latest findings aren’t really that surprising.

Male dolphins in Shark Bay exhibit a fascinating social system of nested alliance formation,” added Manuela Bizzozzero, lead author of the study at the University of Zurich. “These strong bonds between males can last for decades and are critical to each male’s mating success. We were very excited to discover alliances of spongers, dolphins forming close friendships with others with similar traits.”

The fact that dolphins not only use tools, but they form relationships based off of this tool usage, and these relationships resemble the ones in humans is yet another testament to how intelligent and socially advanced dolphins are.